1. Field of the Invention
The present invention relates to a method and an apparatus for testing semiconductor wafers by means of a temperature-regulated chuck device.
2. Description of Related Art
As is known, test measurements on semiconductor wafers are typically carried out in a temperature range between −60° C. and +400° C. For the purpose of temperature control, a semiconductor wafer is placed on a prober table or chuck, which is cooled and/or heated in accordance with the desired temperature.
In this case, it is firstly necessary to take care that the temperature of the semiconductor wafer does not fall below the dew point of the surrounding gaseous medium, since otherwise condensation of moisture occurs on the semiconductor wafer surface, or icing, which hampers the test measurements or makes them impossible.
Secondly, in the case of test measurements with a high chip power, the problem arises that, in the region of the current flow, the semiconductor wafer is heated locally on the front side above the temperature of the rear side in contact with the chuck since, because of the finite heat transfer resistance between semiconductor wafer and chuck, the dissipation of heat is delayed. Typically, in the case of electrical powers of over 100 W, a local temperature difference of about 90 K between the front side of the semiconductor wafer and the supporting side of the chuck is obtained. This temperature difference disrupts the test measurement, which in particular is intended to specify the isothermal electrical properties of the circuits integrated in the semiconductor wafer. At the same time, at relatively high powers the chips can be heated above a maximum permitted temperature, which is associated with the risk of electrical failure.
FIG. 2 shows a schematic cross-sectional view of an apparatus disclosed by U.S. Pat. No. 5,010,296 for testing semiconductor wafers by means of a temperature-regulated chuck device.
In FIG. 2, reference symbol 6′ designates a chuck device the temperature of which can be regulated. The chuck device 6′ is connected to a drive device 7′, which can bring about a movement in the vertical direction and the plane. Provided above the chuck device 6′ is a probe card 12′, which has probes 1′, for example in the form of fine needles, which are used for the purpose of making contact with integrated circuits on a semiconductor wafer 30′ and carrying out electrical measurements thereon.
Reference symbol 13′ designates a test device, by means of which the probes 1′ can be driven in accordance with predefined test programmes. Likewise capable of being driven by the test device 13′ is the control device 7′, in order to connect specific integrated circuits of the semiconductor wafer 30′ to the probes 1′.
A gas feed device 8′, which is connected to a gas supply device 10′, is provided on one side of the chuck device 6′.
On the opposite side of the chuck device 6′, a suction line device 9′ is provided, which is in turn connected to a suction device 11′. The gas feed device 8′ and the suction line device 9′ have a relatively flat cross-sectional shape, so that gas can be flushed uniformly over the entire surface of the semiconductor wafer 30′. The gas flush in this known semiconductor wafer testing apparatus is used to transport away contamination particles which are deposited on the surface of the semiconductor wafer as a result of external influences or under the influence of the probes 1′.
The structure of probe cards for testing semiconductor wafers is known from Elektronik, Produktion und Prütftechik [Electronics, Production and Testing Technology], July/August 1982, pages 485 to 487, Positionieren und Kontaktieren von Halbleiterwafern [Positioning and making contact with semiconductor wafers].
EP 0 438 957 B1 discloses a testing apparatus for semiconductor—semiconductor wafers, a large number of temperature sensors being fitted to a chuck device, which register a corresponding temperature distribution on the chuck surface.
EP 0 511 928 B1 discloses a chuck device having a large number of labyrinth channels, through which a fluid for the temperature control of the chuck device is led. As a result of the labyrinthine structure, a high cooling capacity and a homogeneous temperature distribution are achieved.